1. Field
The present disclosure relates to a common mode filter.
2 . Description of Related Art
As technology advances, electronic devices such as mobile phones, home appliances, personal computers (PC), personal digital assistants (PDA), and liquid crystal displays (LCD) have changed to use a digital operating scheme, rather than an analog operating scheme. As a result, processing speeds thereof have increased in concert with an increase in data throughput. Thus, USB 2.0, USB 3.0, and high definition multimedia interfaces (HDMI) have come into widespread use as high-speed signal transmission interfaces, and such interfaces have been used in a range of digital devices, such as personal computers and digital high-definition television sets.
Such high-speed interfaces commonly employ a differential signal system in which differential signals are transmitted, for example using differential mode signals, across a pair of signal lines. These interface contrast with single-end transmission systems which have been commonly used for a long period of time. Since digitized and high-speed electronic devices are sensitive to external stimulation, the devices can suffer from signal distortion due to high-frequency noise.
Switching voltages generated in circuits, power noise included in power supply voltages, unnecessary electromagnetic signals or electromagnetic noise, and the like may cause the occurrence of such abnormal voltages and noise. As a means of preventing such abnormal voltages and high-frequency noise from being introduced into circuits, common mode filters (CMF) can be used.
In order to remove common mode noise affecting communications sensitivity in mobile devices, common mode filters are often expected to have broadband attenuation characteristics in a communications frequency band of 0.7 GHz to 2.6 GHz.
A common mode filter having a shunt electrode structure has previously been proposed to secure such broadband attenuation characteristics. However, such a common mode filter does not generally provide sufficient attenuation characteristics in a low-frequency domain.